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The Princeton Longevity Center Medical News

The Secret to Low-Carb Diets – Protein Makes You Fuller

By: John Rumberger MD, FACC

People apparently have gotten tired of cutting carbs – Atkins Nutritionals (The Atkins Diet Revolution) filed for Chapter 11 bankruptcy protection July 31, 2005.  Other similar diets, such as the South Beach and the Zone have also seen a decline in popularity.

Just as the air is deflating from the “low carb” diet craze, scientists are figuring out why they seem to work for some people.  The secret isn’t from cutting out carbohydrates from your diet – but the added protein to replace the carbs.  The key is to allow people to feel full, but take in lower amount of calories.  The simplistic view is that individuals have conscious control over appetite and body-weight regulation, which is not the case for most people.  A new study suggests protein suppresses the appetite and by producing satiety, less total calories are consumed.

The Atkins Diet, the South Beach, and the Zone result in an increase in the percent of protein in the diet to about 30-40%.  Until recently, most national dietary guidelines (American Heart Association) have recommended keeping calories from protein at only 10-20% of the diet.  The latest research, published in the American Journal of Clinical Nutrition, suggests that many dieters have been wasting their money on all those low-carb products and focusing on the wrong part of the equation for weight loss.
In the latest study, researchers at the University of Washington School of Medicine put volunteers on three eating regimens.  First, for two weeks, subjects ate a weight-maintaining (neutral calories) with 15% of calories from protein, 35% from fat and 50% from carbs.  Next, for two weeks they tried a high-protein plan with exactly the same number of calories: 30% from protein, 20% from fat and 50% from carbs.  Participants reported being less hungry on this high-protein diet – but because the number of calories per day was unchanged, they did not lose weight.

Finally, for the next 12 weeks the volunteers were told to take in as many calories as they liked, as long as their intake stuck to that high protein, low fat ratio.  Even though there was no ceiling on their calories, during this period the subjects actually reduced their eating by an average of 441 calories per day.  They lost on average 10.8 pounds in body weight and 8.2 pounds in fat mass.  A reduction in 400 calories per day results, if carried out for one year, in a 42 pound weight loss!

These results suggest that protein is more satiating that is fat, and previous studies have shown that protein is more satiating than carbohydrates.  Thus, encouraging our patients to eat increasing more lean meat and low-fat dairy products may ultimately encourage them to eat fewer calories and thus to lose weight.  Scientists don’t know yet why protein makes you feel fuller than other foods, but there is a large trial beginning in Europe.  The DiOGenes (diet, obesity, and genes) project will investigate the effect of high-protein diets for one year on 1,500 to 3,000 individuals.  It may provide some answers as well as testing concerns about any potential adverse health effects of a high protein diet.

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